Strange cycle

Ok so opinions please, last month my husband and I bd on multiple o days. Then out of no where I started spotting dark dark brown 11 days before my period. It turned into dark red but not like a normal period. No cramps what so ever no sore breasts, nothing. Lasted 6 days then stopped. I am now 2 days past my original period start date. Could that have been implantation bleeding? I thought it was too heavy I did use a tampon... I'm just confused never had that happen during a cycle and now I'm late for my regular period. Any opinions or advice or any stories similar? Thank you all in advance!